A circuit assembly provided in a vehicle-mounted electrical junction box (substrate unit) is disclosed in JP 2003-164039A, for example. This circuit assembly is provided with a connector to be connected to an external wiring material (counterpart connector portion), and the connector is constituted by a terminal that is provided at an end of a busbar component plate bonded to the lower side of a control circuit board, and a housing that is formed in one piece with a case around the busbar component plate and surrounds the terminal. A heat dissipation member (bottom portion) is bonded to the lower sides of the busbar component plate and the case using an adhesive (bonding layer).